ym-dl-watcher/internal/yandex/client.go

package yandex

import (
	"context"
	"crypto/md5"
	"encoding/hex"
	"encoding/xml"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"os"
	"strings"
	"time"

	"ym-dl/internal/config"
	"gitea.mrixs.me/Mrixs/yandex-music-api-go/yandexmusic"
)

const downloadSalt = "XGRlBW9FXlekgbPrRHuSiA" // Magic salt for URL signing

// TrackPosition represents track position in album
type TrackPosition struct {
	Volume int `json:"volume"`
	Index  int `json:"index"`
}

// YandexClient wraps the external yandexmusic client
type YandexClient struct {
	client     *yandexmusic.Client
	config     *config.YandexConfig
	httpClient *http.Client
	debug      bool
	logger     *slog.Logger
}

// NewYandexClient creates a new Yandex Music client wrapper
func NewYandexClient(cfg *config.YandexConfig, debug bool) (*YandexClient, error) {
	if cfg.Token == "" {
		return nil, errors.New("yandex.token is required")
	}

	httpClient := &http.Client{
		Timeout: 30 * time.Second,
	}

	logLevel := slog.LevelInfo
	if debug {
		logLevel = slog.LevelDebug
	}
	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
		Level: logLevel,
	}))

	client := yandexmusic.NewClient(yandexmusic.ClientConfig{
		Token: cfg.Token,
	})

	if err := client.Init(context.Background()); err != nil {
		return nil, fmt.Errorf("init client: %w", err)
	}

	return &YandexClient{
		client:     client,
		config:     cfg,
		httpClient: httpClient,
		debug:      debug,
		logger:     logger,
	}, nil
}

// GetArtistTracks fetches tracks for an artist
func (c *YandexClient) GetArtistTracks(ctx context.Context, artistID int, page, pageSize int) ([]*yandexmusic.Track, error) {
	result, err := c.client.GetArtistTracks(ctx, fmt.Sprintf("%d", artistID), page, pageSize)
	if err != nil {
		return nil, err
	}
	tracks := make([]*yandexmusic.Track, 0, len(result.Tracks))
	for i := range result.Tracks {
		tracks = append(tracks, &result.Tracks[i])
	}
	return tracks, nil
}

// GetArtistAlbums fetches albums for an artist
func (c *YandexClient) GetArtistAlbums(ctx context.Context, artistID int, page, pageSize int) ([]*yandexmusic.Album, error) {
	result, err := c.client.GetArtistAlbums(ctx, fmt.Sprintf("%d", artistID), page, pageSize)
	if err != nil {
		return nil, err
	}
	albums := make([]*yandexmusic.Album, 0, len(result.Albums))
	for i := range result.Albums {
		albums = append(albums, &result.Albums[i])
	}
	return albums, nil
}

// GetAlbumWithTracks fetches an album with its tracks
func (c *YandexClient) GetAlbumWithTracks(ctx context.Context, albumID string) (*yandexmusic.Album, error) {
	albums, err := c.client.GetAlbumsWithTracks(ctx, []string{albumID})
	if err != nil {
		return nil, err
	}
	if len(albums) == 0 {
		return nil, fmt.Errorf("album not found")
	}
	return albums[0], nil
}

// GetTrackInfo fetches a single track's info
func (c *YandexClient) GetTrackInfo(ctx context.Context, trackID string) (*yandexmusic.Track, error) {
	return c.client.GetTrack(ctx, trackID)
}

// GetTrackInfoWithPosition fetches track info including track position in album
func (c *YandexClient) GetTrackInfoWithPosition(ctx context.Context, trackID string) (*yandexmusic.Track, *TrackPosition, error) {
	track, err := c.client.GetTrack(ctx, trackID)
	if err != nil {
		return nil, nil, err
	}

	// Extract track position from first album
	var position *TrackPosition
	if len(track.Albums) > 0 {
		albumID := string(track.Albums[0].ID)
		albums, err := c.client.GetAlbumsWithTracks(ctx, []string{albumID})
		if err == nil && len(albums) > 0 {
			album := albums[0]
			// Find track in album.Volumes and get position
			for volIdx, volume := range album.Volumes {
				for trackIdx, t := range volume {
					if string(t.ID) == trackID {
						position = &TrackPosition{
							Volume: volIdx + 1,
							Index:  trackIdx + 1,
						}
						break
					}
				}
				if position != nil {
					break
				}
			}
		}
	}

	return track, position, nil
}

// GetTrackDownloadInfo gets download info for a track
func (c *YandexClient) GetTrackDownloadInfo(ctx context.Context, trackID string) ([]yandexmusic.DownloadInfo, error) {
	return c.client.GetTrackDownloadInfo(ctx, trackID, "")
}

// GetArtistInfo fetches artist info
func (c *YandexClient) GetArtistInfo(ctx context.Context, artistID int) (*yandexmusic.Artist, error) {
	return c.client.GetArtist(ctx, fmt.Sprintf("%d", artistID))
}

// DownloadTrackXML downloads the XML with track download URLs
func (c *YandexClient) DownloadTrackXML(ctx context.Context, downloadInfoURL string) ([]byte, error) {
	req, err := http.NewRequestWithContext(ctx, "GET", downloadInfoURL, nil)
	if err != nil {
		return nil, fmt.Errorf("create download XML request: %w", err)
	}

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("download XML request: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("download XML failed: %s: %s", resp.Status, string(body))
	}

	return io.ReadAll(resp.Body)
}

// DownloadInfoXML describes the structure of the XML file with download info
type DownloadInfoXML struct {
	XMLName xml.Name `xml:"download-info"`
	Host    string   `xml:"host"`
	Path    string   `xml:"path"`
	Ts      string   `xml:"ts"`
	S       string   `xml:"s"`
}

// GetTrackDownloadURL gets the direct MP3 download URL for a track
func (c *YandexClient) GetTrackDownloadURL(ctx context.Context, trackID string) (string, error) {
	// Get download info to find best MP3 quality
	downloadInfos, err := c.GetTrackDownloadInfo(ctx, trackID)
	if err != nil {
		return "", fmt.Errorf("get download info: %w", err)
	}

	// Find best quality MP3
	var bestInfo *yandexmusic.DownloadInfo
	for _, info := range downloadInfos {
		if info.Codec == "mp3" && info.DirectLink {
			if bestInfo == nil || info.Bitrate > bestInfo.Bitrate {
				bestInfo = &info
			}
		}
	}
	if bestInfo == nil {
		for _, info := range downloadInfos {
			if info.Codec == "mp3" {
				if bestInfo == nil || info.Bitrate > bestInfo.Bitrate {
					bestInfo = &info
				}
			}
		}
	}
	if bestInfo == nil && len(downloadInfos) > 0 {
		bestInfo = &downloadInfos[0]
	}
	if bestInfo == nil {
		return "", fmt.Errorf("no suitable download info found")
	}

	if c.debug {
		for i, info := range downloadInfos {
			c.logger.Debug("download info candidate", "index", i, "codec", info.Codec, "bitrate", info.Bitrate, "direct_link", info.DirectLink, "url", info.URL)
		}
	}

	// If we have a direct URL, use it
	if bestInfo.URL != "" && bestInfo.DirectLink {
		return bestInfo.URL, nil
	}

	// If we have a download info URL, use it to get the signed URL
	if bestInfo.URL != "" {
		// Download and parse XML
		xmlData, err := c.DownloadTrackXML(ctx, bestInfo.URL)
		if err != nil {
			return "", fmt.Errorf("download XML: %w", err)
		}

		var infoXML DownloadInfoXML
		if err := xml.Unmarshal(xmlData, &infoXML); err != nil {
			return "", fmt.Errorf("parse XML: %w", err)
		}

		// Generate signed URL
		signData := []byte(downloadSalt + strings.TrimPrefix(infoXML.Path, "/") + infoXML.S)
		sign := md5.Sum(signData)
		hexSign := hex.EncodeToString(sign[:])

		finalURL := fmt.Sprintf("https://%s/get-mp3/%s/%s%s", infoXML.Host, hexSign, infoXML.Ts, infoXML.Path)

		if c.debug {
			c.logger.Debug("constructed download URL", "url", finalURL)
		}

		return finalURL, nil
	}

	return "", fmt.Errorf("no download URL available: bestInfo.URL is empty (codec=%s, bitrate=%d, direct_link=%v)", bestInfo.Codec, bestInfo.Bitrate, bestInfo.DirectLink)
}